JPH02204910A - Insulated cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a crosslinked polyolefin resin insulated cable with excellent long-term stability.

<Prior Art> Conventionally, in addition to OF cables, crosslinked polyolefin resin cables have been used as insulated cables.

Crosslinked polyolefin resin cables are being widely used in place of OF cables because they are easy to maintain and have low power transmission loss.

However, this crosslinked polyolefin resin cable has the disadvantage that it is inferior to that of the OF cable in terms of long-term stability, and various studies have been made to improve this disadvantage.

Moisture is cited as one of the factors that affects the long-term stability of crosslinked polyolefin resin cables. When moisture is present in the insulator, it collects in high electric field areas such as foreign objects, voids, and irregularities at the interface between the insulator and the internal and external semiconducting layers, forming conductive branches called water trees. It is known that this leads to the formation of a channel, which eventually leads to dielectric breakdown.

For this reason, insulated cables are also used that have a structure in which a metal layer is provided on the outside of the insulator to prevent moisture from the external environment from penetrating into the insulator.

Furthermore, the crosslinking method has changed from a method using high-pressure steam as a heat medium to a method called dry crosslinking that does not use steam, such as heating with a heater or using heated gas.

<Problems to be Solved by the Invention> An organic peroxide having a crosslinked polyolefin group (where n=1 or 2) used in conventional insulated cables is used.

However, when dicumyl peroxide or 1,3-bis(tertiary-butylperoxyisopropyl)benzene is used as a crosslinking agent having such a group in its molecule, it decomposes when heated at high temperature for a long time. It is known that moisture is generated as a residue, and even if the structure does not allow moisture to enter from the outside, there is a problem in that moisture is generated in the insulator.

That is, when dicumyl peroxide is heated at high temperature for a long time, it generates water (020) as shown in the formula below, and 1,3-bis(tertiary-butylperoxyisopropyl)benzene also generates moisture (020) as shown in the formula below. When heated at a high temperature for a long time, as shown in the formula below, when an organic peroxide such as (tertiary-butylperoxyisopropyl)benzene is used as a crosslinking agent in an insulated cable with a fin-based resin as an insulating layer, It is necessary to suppress the generation of moisture (as a result of examination, there was a problem that it generates moisture.

For this reason, crosslinking agents such as dicumyl peroxide and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne3 other than 1,3-bis(tert-butylperoxyisopropyl)benzene are used. However, such crosslinking agents are more expensive than dicumyl peroxide and 1,3-bis(tertiary-butylperoxyisopropyl)benzene, and have lower crosslinking efficiency, making them impractical. Ta.

Means for Solving the Problems> In view of the above points, the present inventors used an organic peroxide having a crosslinked polyole (n=1 or 2) as a crosslinking agent and an aromatic amide additive. By using a crosslinked polyolefin resin as an insulating layer, an insulated cable with excellent long-term stability is provided.

Effects> As described above, this invention uses an organic peroxide having a crosslinking agent 2) and also uses an aromatic amide as an additive to obtain a crosslinked polyolefin resin constituting an insulating layer. The purpose is to suppress the generation of water, which is a decomposition residue of such a crosslinking agent.

Any one type or two or more types of acrylate groups, (
However, when using an organic peroxide having n=1 or 2), for example dicumyl peroxide, its decomposition product, cumyl alcohol, is further decomposed to produce water, and also as a crosslinking agent. When using 1,3-bis(tert-butylperoxyisopropyl)benzene, its decomposition product 1,3-bis(2-
Hydroxy-2-propyl)benzene further decomposes to produce water, so when using these crosslinking agents, if an aromatic amide is also used as an additive, cumyl alcohol and 1. 3-bis(2
It is thought that the decomposition of -hydroxy-2-propyl)benzene is suppressed.

In this invention, the polyolefin resins include low-density polyethylene produced by high pressure method or low pressure method, ethylene-vinyl acetate, ethylene ethyl acetate (however, n=1 or 2).
) as the organic peroxide type crosslinking agent, dicumyl peroxide or 1,3-bis(tertiary)
butylperoxyisopropyl)benzene is preferred;
The amount of these crosslinking agents added should be such that the degree of crosslinking of the polyolefin resin is appropriately obtained (preferably 1.0 to 3.0% by weight).

Further, as the aromatic amide which is an additive, an aromatic organic acid amide can be used, and specific examples thereof include benzamide, naphthamide, benzenesulfonamide and the like.

If the amount of aromatic amide added is less than 0.01% by weight, it will not be possible to suppress the generation of moisture from the crosslinking agent, and if it exceeds 2% by weight, blooming will occur on the surface of the uncrosslinked polyolefin resin pellet before cable processing. 0.01 because this will cause the extrusion process to be unable to be carried out stably.
It is preferably within the range of 2% by weight.

The crosslinked polyolefin resin insulator in this invention may include 4,4-thiobis(6-tert-butyl-3-methylphenol) or tetrakis[methylene-3].
Additives such as an antioxidant such as -(3',5'-di-tert-butyl-41-hydroxyphenyl)propionate]methane may be blended.

As mentioned above, the present invention relates to an insulated cable using a crosslinked polyolefin resin containing a specific organic peroxide and an aromatic amide as an additive in the insulating layer, but the decomposition residue of the crosslinking agent volatilizes. This invention is particularly effective when forming an insulating layer with a thickness of 7 to 35 mn+, which is difficult.

In addition, in recent years, insulated cables have generally been provided with a metal water-shielding layer to prevent moisture from entering from the outside.While this metal water-shielding layer has the effect of preventing moisture from entering from the outside, it There is a problem in that it prevents moisture generated inside the layer from volatilizing to the outside.

In the insulated cable of the present invention, since the amount of water in the insulating layer 2 is small, the effect is particularly remarkable when a metal water-blocking layer is provided on the outside.

<Example> Hereinafter, this invention will be explained in detail with reference to Examples.

Example 1 A polyolefin resin having the physical properties such as density and melt flow rate shown in Table 1 was used, and
As shown in Table 3, dicumyl peroxide is used as a crosslinking agent, and an aromatic amide such as p-n-butylbenzamide or naphthamide is added as an additive.
After mixing for 5 minutes using a hot roll at 0°C, an uncrosslinked sheet with a thickness of 20 mm was created using a hot press at 120°C.

After dry heating these uncrosslinked sheets at 220°C for 60 minutes under a pressure of 5 kg/cm of nitrogen gas, the sheets were taken out and the moisture content was measured by sampling from the center of the sheet. was carried out by Karl Fischer trace moisture measurement method.

The results are shown in Tables 2 and 3.

From the above table, sample No. 1- without adding aromatic amide
50 for 1.19, 1-12, and 1-15
0 ppm or more of water is generated, and even when the amount of aromatic amide is less than the range of the present invention (sample No. 1-2), a large amount of water (460 ppm) is generated.
．． In the examples of the present invention in which an aromatic amide within the range of 0.01 to 2% by weight was added, the water content was 30 ppm or less, and it was observed that the generation of water was significantly suppressed.

In addition, blooming was observed on the surface of sample No. 1-7 in Table 2 due to the large amount of aromatic amide.

Example 2 The insulating layer was made of a material prepared by blending the high-pressure low-density polyethylene resin shown in Table 1 of Example 1 with the crosslinking agent and aromatic amide shown in Table 4, and a semiconductive resin in which carbon was dispersed was used inside and outside. A cable having an outer semiconductive layer was processed by a three-layer simultaneous extrusion method at 120° C., and this cable was subjected to a crosslinking process for about 60 minutes at 220° C. under a pressure of 5 kg/am 2 of nitrogen gas to obtain an insulated cable.

Next, a sample was taken from the center of the insulating layer of this insulated cable to measure the moisture content. The results are shown in Table 4.

Example 3 A crosslinked sheet was prepared in the same manner as in Example 1 except that 13-bis(tertiary-butylperoxyisopropyl)benzene was used as the crosslinking agent in place of dicumyl peroxide in Example 1, and further water was removed. The amount was measured.

The results are shown in Tables 5 and 6.

From the above table, sample No. 3- does not contain aromatic amide.
1.3-9, 3-12, and 3-15, 5
When moisture of 00 ppm or more is generated and the amount of aromatic amide is less than the range of the present invention (sample No. 3-2)
A large amount (350 ppm) of water is generated in
In the examples of the present invention in which an aromatic amide within the range of 0.001 to 2% by weight was added, the water content was 30 ppm or less, and it was observed that the generation of water was significantly suppressed.

In addition, blooming was observed on the surface of sample No. 3-7 in Table 5 due to the large amount of aromatic amide.

<Effects of the Invention> As explained above, the insulated cable having the crosslinked polyolefin resin insulating layer of the present invention has excellent long-term stability as the insulating layer significantly suppresses the generation of moisture due to heating. It can be used as an insulated cable with high electric fields.

Claims (5)

[Claims] (1) There are ▲ mathematical formulas, chemical formulas, tables, etc. in the molecule ▼ groups,
An insulated cable characterized in that an insulating layer is made of a polyolefin resin crosslinked using an organic peroxide having the formula (where n=1 or 2) as a crosslinking agent and an aromatic amide as an additive. (2) There are ▲ mathematical formulas, chemical formulas, tables, etc. in the molecule ▼ groups,
Claim (1) characterized in that the organic peroxide having (n=1 or 2) is dicumyl peroxide.
Insulated cable as described. (3) There are ▲ mathematical formulas, chemical formulas, tables, etc. in the molecule ▼ groups,
(however, n=1 or 2) is an organic peroxide having 1,3
The insulated cable according to claim 1, characterized in that the insulated cable is made of shari-butylperoxyisopropyl)benzene. (4) The insulated cable according to claim 1, (2) or 3, wherein the aromatic amide is used in an amount of 0.01 to 2% by weight. (5) As the polyolefin resin, any one of high-pressure low-density polyethylene, low-pressure low-density polyethylene, ethylene vinyl acetate, and ethylene ethyl acrylate
A claim characterized in that a species or two or more species are used (
1) Insulated cable as described.